Filter Cake Build-Up and Backwashing
Particle deposition by sieving, filter cake build-up and re-entrainment of deposited particles and agglomerates can be simulated by high-precision resolved 2-way CFD-DEM coupling.
By this method, the flow field around each single particle is resolved and the forces which act on a particle are computed by integration of pressures and relative velocities over the particle surface.
The effect of the particles on the fluid flow is taken into account by velocity boundary conditions on the particle surface. By this, volume displacement and momentum transfer from the particles on the fluid are reproduced.
As a less computationally intensive alternative to 2-way CFD-DEM coupling, 1-way CFD-DEM coupling is also available in DNSlab, where the effect of the undeposited particles on the flow is neglected. Thus, the computational effort for the flow calculation can be substantially reduced. At the same time, a wider particle size distribution can be mapped.
The 1½-way CFD-DEM coupling allows the simulation of filter cake buildup and backwashing including the accompanying pressure drop changes, at a relatively low requirement of computation resources. The flow field is only updated when a significant number of particles has deposited or detached, so that the flow field does not have to be updated in each time step.
